Thermophysical properties of Cordyceps militaris change during the freezing process

Abstract

This study focuses on determining the thermophysical parameters of Cordyceps militaris in the freezing stage of the freeze-drying process. When the temperature of Cordyceps militaris changed from an ambient temperature of 25°C to a freezing temperature of -45°C, the thermophysical parameters of Cordyceps militaris changed much. The study determined the initial freezing point temperature of Cordyceps militaris to be -0.6°C. At temperatures above the initial freezing point, the density (ρ) and specific heat (c) increase slightly as the temperature decreases. In contrast, thermal conductivity (k), thermal diffusivity (a), and enthalpy (h) decrease. However, at temperatures below the initial freezing point, when the temperature decreases, the density, specific heat, and enthalpy decrease while the coefficient of thermal conductivity and thermal diffusion increase. The results obtained from this study can be applied in calculating the heat and mass transfer during the freezing phase in the freeze-drying process of Cordyceps militaris.